Example:
cat README.md | codedown haskell --separator=----- --section 1.3
`

Codedown reads Markdown from stin, extracts the code blocks designated
as language , and outputs them to stdout. The example above
extracts the Haskell code from section 1.3 of this file, and outputs it
with five dashes in between each block:

`
x :: Int
x = 42
-----
main :: IO ()
main = putStrLn $ show x
`

We can pipe the output of Codedown to a language interpreter:

`
$ cat README.md | codedown haskell | runhaskell
42
`

`
$ cat README.md | codedown javascript | node
42
`

`
$ cat README.md | codedown scala | xargs -0 scala -e
42
`

Examples

This readme is a Markdown file, so we can use Codedown to extract code
from it.

$3

In the following code blocks, let's set x to 42 in different
languages:

Haskell:

`haskell
x :: Int
x = 42
`

JavaScript:

`javascript
var x = 42;
`

Scala:

`scala
val x = 42
`

$3

Now let's print x it to stdout in different languages. This time, the
code blocks are nested within an unordered list:

Haskell:*

`haskell
main :: IO ()
main = putStrLn $ show x
`

JavaScript:*

`javascript
console.log(x);
`

Scala:*

`scala
println(x)
`

$3

Build and run a Docker image:

`
docker build -t codedown:dev .
`

Use it to extract haskell code blocks and save to output.hs:

`
cat README.md | docker run -i codedown:dev haskell > output.hs
`

Sections and subsections

The section above is 1.3, counting by headings. It has two subsections
(1.3.1 and 1.3.2). We can specify a section number to extract the
content from just that section:

`
$ cat README.md | codedown haskell --section 1.3
x :: Int
x = 42

main :: IO ()
main = putStrLn $ show x
`

`
$ cat README.md | codedown haskell --section 1.3.1
x :: Int
x = 42
`

`
$ cat README.md | codedown haskell --section 1.3.2
main :: IO ()
main = putStrLn $ show x
`

We can also specify a section by heading:

`
cat README.md | ./codedown.js haskell --section '### Variables in different languages'
x :: Int
x = 42
`

Wildcard matching

Codedown can use wildcards to match file paths, which are used by some
markdown implementations:

lib/codedown.js:

`lib/codedown.js
var x = 42;
`

`
$ cat README.md | codedown '*/.js'
var x = 42
`

Additionally, you can use a special * character in place of the language
option to extract any/all code blocks agnostic of language:

`
$ cat README.md | codedown '*'
`

Separator

If there are multiple code blocks in the same file, we can specify a
separator to insert in between them:

`
$ cat README.md | codedown haskell --separator=-----
x :: Int
x = 42
-----
main :: IO ()
main = putStrLn $ show x
``